Rust
I can still explain how to do it.
The steps and the sequence.
But when I tried it again after years away, my hands didn't listen.
The mind remembered.
The body had moved on.
We assume knowing is enough.
That understanding locks in permanently once it arrives.
It doesn't.
Unused skills rust. Lessons that never leave the page fade into trivia.
You end up able to describe the thing without being able to do it.
The difference between knowing and capability is repetition.
One lives in your head.
The other has to live in your hands.
You can explain how to ride a bike without being able to ride one. The body forgets what the mind still remembers.